My setup is a Dreamcast with a 1 on the bottom, USB-GDROM, Pico PSU, and 40mm fan connected to the 12 volt rail with pull up resistor. I have not yet replaced my system battery but have new batteries in my VMU.
When I turn on my Dreamcast after it being off for a prolonged period it usually starts up fine but sometimes prompts for time and date. This is normal behavior for an old system battery. The weird part is if I play for a period of 15 plus minutes then turn the console off then back on to play a different game it does the following sequence. Enter Date and Time -> Enter Date and Time again -> launch disk from system menu -> Disc appears to load but instead of the game I'm sent to enter date and time -> Enter Date and Time -> Enter Date and Time -> over and over again until I power off the system for a period of about a half hour. I can't find anything online. Does this sound like it would be a battery issue or something more? I've ordered a new battery and controller board to swap. I thought maybe the date and time needed to match my VMU but that doesn't seem to matter.